Abstract (Invited)

Generalized Acoustic Nonlinearity Parameters for Solids, Fluids, and Biological Media

J.H.Cantrell (NASA Langley Research Center, Hampton, VA, USA)

e-mail: j.h.cantrell@larc.nasa.gov

In the derivation of the nonlinear wave equation for liquids the isentropic equation of state is usually expanded in a power series with respect to the mass density of the fluid. It is shown that the strain measure, the fractional change in the mass density with respect to the unperturbed mass density, traditionlly used in the expansion is inconsistent with finite deformation theory and that the commonly used parameter B/A, obtained from the expansion, does not properly characterize acoustic nonlinearity in liquids. A new model based on the strict application of finite deformation theory with consideration of the crystallographic structure of the material is proposed that leads to a unified description of acoustic nonlinearity for solids, fluids, and biological materials. The unified theory provides for the definition of a common generalized acoustic nonlinearity parameter that includes the effects of initial stresses to facilitate comparison of acoustic nonlinearity in propagation media of arbitrary crystalline structure and phase.

Section : 2